Some printers or printing systems of today have been known for having a print enlargement function (hereinafter, referred to as a “poster printing function”) of enlarging and dividing an image on a page so that a resultant image is printed over several sheets of paper. With this function, an output of the enlarged image can be obtained by combining sheets of paper delivered in an order according to a manner of dividing the image.
However, the poster printing function provided in the conventional printers only supports single-sided printing, and printers having both a double-sided printing function and the poster printing function have not been realized. This is probably because an arrangement of papers on which a divided image is printed is different between front and back sides under double-sided poster printing, which should be considered carefully to obtain an accurate output result.